The present invention relates to a process for grinding a gear tooth blank to form an involute gear tooth, and more particularly to a process for grinding a gear tooth blank at constant cutting rate to form an involute gear tooth.
Most precision gears for use in the industry are involute gears. Referring to FIG. 1, in common practice, to grind a gear tooth blank to form an involute gear tooth, the gear tooth blank effects a constant angular displacement prior to each grinding stroke during which it is ground by a grinding wheel which moves across the space between two gear teeth of the gear blank. The rotational angle for each grinding stroke is designated at B. Since the angular displacement for each grinding stroke is a constant, the removed area of one tooth face of the gear blank during each grinding stroke is variable within a broad range, as shown in FIG. 2. This largely variable cutting rate causes the action force between the grinding wheel and the workpiece, i.e. the cutting force, to vary within a broad range, as shown in FIG. 3. Further, this largely variable cutting force may result in the partial deformation of the abrasive grains of the grinding wheel and in the undesired displacement between the workpiece and the grinding wheel during grinding operation, thereby resulting in the errors of the involute, the tooth profile, and the pitch, as shown in FIG. 4. Additional machining is needed which results in a lower rating of production.
In addition, since the center of each gear tooth blank is generally located at an eccentric distance in relation to the center of the gear blank, the metal removal amount for respective grinding strokes is largely varied. The errors of the involute, the tooth shape, and the pitch thus become uncontrollable. When some of these errors are irreconcilable, the gear may become useless.